Project Summary With the advancement of medical treatments, which has contributed to the overall decrease in opportunistic infections and deaths related to human immunodeficiency virus (HIV) in youth, there is a need to ensure that youth living with HIV (YLH) are linked to and engaged in care to successfully achieve viral suppression. While an increasing number of mobile health (mHealth) technologies have been designed to address HIV prevention and care, a critical gap in innovation remains in tools designed to address the specific needs of YLH. In a Phase I project, we demonstrated the acceptability and feasibility of a user-centered prototype design of PlusCare, an mHealth application that can be used by YLH and their case managers (CMs) to support HIV care. Results of Phase I suggest that PlusCare could facilitate multi-disciplinary, team-based case management of YLH by supporting the sharing and signing of documents remotely, automation of adherence reminders, sharing of lab results, alerts CMs about program requirements related to age and developmental milestones, streamlining of communication between multiple members of a patient?s case management team and the patient, and offering accessibility to data from multiple modalities. In this Phase II project, we will directly test and demonstrate the effectiveness of PlusCare on HIV case management processes and care continuum outcome measures for YLH. We will accomplish this objective in the following 3 specific aims: 1) Enhance PlusCare for generalizability across clinical settings in a formative assessment in Substudy 1 with CMs (N=5) and their YLH patients between the ages of 13-25 years old (N=10) at a new site; 2) Build and demonstrate usability of an enhanced, fully functional system with rapid, iterative usability testing in Substudy 2 with CMs (N=10) and patients (N=10); and 3) Conduct a mixed methods, non-randomized pre-post study in Substudy 3 with CMs (N=20) and patients (N=70) to evaluate the effectiveness of PlusCare of case management processes and health outcomes (i.e., HIV viral load, medical visit frequency and gaps) in 3 different case management programs at 2 different clinical sites. An initial cost analysis will be performed to assess potential cost effectiveness Results of these Phase I and II projects will validate a product that can be used in multiple case management settings and prepare PlusCare for commercialization in a potential Phase III. Results have implications for future development of PlusCare to serve the broader HIV population (YLH aged 25-34 years old and at-risk individuals) as well as youth living with other chronic health conditions.